Plotly[
{x, x * 0.87, Which[
14 * x < 2400000,
x * 0.87,
14 * x < 5000000,
200000 * 0.87 + (x - 200000) * 0.85,
True, 200000 * 0.87 + 157142 * 0.85 + (x - 357142) * 0.82
]},
{x, 0, 500000}, ImageSize -> 1200
]